By virtue of their very wide range of chemical and physical properties, monoamines and polyamines are used as reactants in a variety of different chemical reactions. Reference is merely made here to their catalytic activity in numerous chemical reactions attributable to their basicity and to their use as crosslinking agents for polyurethane and epoxide resins. For many applications, it is desirable not to use the free amines, but instead to add the amines to the reaction mixture in a masked form from which they are released at a specific time to initiate the required reaction.
It is possible, for example, to release amines from enamines, ketimines and aldimines by the addition of water. Unfortunately, one disadvantage of these compounds lies in their high sensitivity to moisture; tertiary amine nitrogen atoms cannot be blocked in this way. It is also known that amines can be released from quaternary ammonium salts by heating to above 100.degree. C. (Houben-Weyl, Methoden der Organischen Chemie, Vol. XI, 1). In many cases, however, it is desired to release the amines at considerably lower temperatures.
It has now surprisingly been found that amines can be released from ammonium salts of .alpha.-ketocarboxylic acids, even at room temperature, under the action of light having a wavelength in the range of from about 250 to 500 nm, the ketocarboxylic acid undergoing decarboxylation.